Loss of function in the hand can occur for numerous reasons which include post fracture of the carpal, metacarpal and phalange bones, dislocation and injury of the joints in the hand, tendon injuries, nerve injuries (lesions), vascular impairment due to venous or arterial damage, muscular and skin injury. Causes of these injuries can be due to chronic and acute conditions and also as a result of trauma. Examples include sporting injuries, road traffic accidents, traumatic industrial injury due to crushing, occupational hand disorders such as RSI (Repetitive Strain Injury), VWF (Vibration induced White Finger) and CTS (Carpal Tunnel Syndrome) plus other causes of nerve compression and burns to the hand (thermal, electrical or chemical).
In order to restore function, reduce deformity and reduce pain it is important that regular therapeutic exercises of the hand are undertaken. This is especially important following reconstructive surgery of the hand following complex fractures or burns. Other reasons for applying hand physiotherapy is in the treatment of degenerative chronic diseases such as (RA) Rheumatoid arthritis, degenerative nerve diseases such as MND (Motor Neuron Diseases) and rehabilitation following a stroke (Acute or Chronic).
Some aims in applying hand exercises include improving blood flow, strengthening weakened muscles, reducing oedema and exercising paralysed or contorted fingers. Additionally it has been shown that following a trauma injury, the patient can be affected by Complex Pain Syndrome, which can be more problematic than the initial injury but is less prevalent if regular therapeutic exercises are undertaken.
Although it is recognised that controlled physical therapy can prevent or reduce long term problems such as distortion, contracture, pain and also improve the range of available movement, there are barriers to applying therapy. The conventional type of therapeutic exercises that have been shown to alleviate the above problems have traditionally been administered by a helper or specialist therapist. These types of exercises are commonly referred to as PROM (Passive Range of Movement). To ensure these exercises are effective they must be undertaken several times a day to prevent contracture. Each individual exercise can take at least 30 minutes and with a physical therapist having 10 or more patients to look after this can become impossible to achieve, resulting in patients not receiving the optimum level of therapy to aid their recovery.
In order to overcome this problem several devices have been conceived in order to reduce the time the therapist needs to spend with the patient by encouraging the patient to carry out the exercise themselves. One such device is described in U.S. Pat. No. 6,733,421 for providing the user a means to perform therapeutic hand exercises. Other orthotic devices for treating contracture and providing rehabilitation are described in U.S. Pat. Nos. 6,547,752, 6,673,028, 6,482,168 and 4,907,574. Sometimes it is desirable to exercise individual digits of the hand independently and U.S. Pat. No. 5,413,554 describes a Hand splint and exerciser device that provides a means to apply tension to an individual finger against which the patient applies an opposing force.
Devices utilising pneumatic inflatable elements as a means to assist in moving the joints of the hand are described in U.S. Pat. Nos. 5,593,369, 5,466,202, 3,937,215, 5,437,620, 5,152,740, 3,581,740, 5,020,515, 4,644,938 and 4,274,399. Generally these devices assist the therapist in moving the fingers away from the palm and cannot exercise individual fingers over the full range of possible movement with the patients' joints in a relaxed state. A Therapeutic Multiple Joint Exerciser is described in U.S. Pat. No. 4,671,258, which teaches a method of utilising air bladders and a combination of sprung steel strips to exercise different joints in the body including the hand. An embodiment is described in which the air bladders and compartments for the sprung steel strips is held in place on the dorsal surface of the hand and held in place by straps around the wrist and by straps around the ends of the fingers.
The physical practicalities of using air as an actuation means may have prevented the use of this technology in a commercial device. Because of the compressible nature of air, in order to generate sufficient force to extend a finger, either a small volume of high pressure air or a large volume of lower pressure air is required. High pressure is not desirable in this application and therefore the volume of the bladder needs to be maximised. In U.S. Pat. No. 4,671,258, large air bladders are described that extend beyond the length of the fingers, which in clinical utility may have some significant practical issues in patient compliance and likely prevent use of the hand for normal activities whilst in use on the hand. A pumping unit suitable for providing an air supply for such a pneumatic exercise device is described in U.S. Pat. No. 4,763,893.
U.S. Pat. No. 4,619,250A describes a therapeutic aid for treatment of the symptoms of carpal tunnel syndrome and similar conditions associated with nerve impairment. A device is described that consists of a wrist splint cloth that has bladders for liquid or air incorporated into the spaces between the fingers. The device utilises a separate pump and control system for inflating and deflating the bladders. Separate bladders are provided for extending and contracting the fingers.
Devices that also administer automatic therapy and do not require the patient to use their own muscles are known as CPM (Continuous Passive Motion) Devices. Generally these devices only require assistance from a therapist in setting the device up. Devices that fall into this category are described in U.S. Pat. Nos. 4,619,250, 4,576,148, 3,937,215, 4,875,469, 5,765,228 and 5,261,393. The CPM devices in general use are typically complex electro-mechanical devices that require significant and skilled setting up, can reduce the mobility of a patient and are often very expensive.
An alternative means of providing an actuation force to straighten the fingers is described in EP421368 and uses an electrical current and a control circuit to intermittently heat a temperature sensitive memory alloy which provides a cyclic exercise. Generally the cost of memory alloys and their associated control systems have precluded them from widespread commercial use.
Each of the prior art devices identified is only intended to provide one of Continuous Passive Motion Therapy (automatic exercise) or Passive Motion Therapy (driven by the patient). The devices are generally not easily portable, tend to be expensive and do not generally promote patient compliance with clinical treatment programmes. Therefore there is a need for a therapeutic hand exercise device which reduces or substantially obviates these problems.